brush tool any longer. The paintbrush, airbrush and pencil
tools, which already knew how to handle the single-pixmap
brushes now also handle the pipes as well.

* app/pixmapbrush.{h,c}
* app/gimpbrushpixmap.{h,c}: Removed these files.

* app/Makefile.am
* app/makefile.{cygwin,msc}: Remove from here, too.

* app/gimpbrushpipe.{h,c}: Total overhaul.

* app/paint_core.h
* app/apptypes.h: Some more types moved to apptypes.h

* app/context_manager.c
* app/tool_options.c
* app/tools.c
* app/toolsF.h: Remove PIXMAPBRUSH tool.

* app/gimpbrush.h: New method: select_brush. Used to change the
brush in paint_core, for pipe brushes.

* app/gimpbrush.c: Add gimp_brush_select_brush, which is dummy for
the normal brushes (returns the same brush).

* app/paint_core.c: Call the brush's select_brush method to get a
potential new brush before calling the paint_func.

* app/gimpbrushlist.c: Various changes related to the pixmap and
pipe overhaul.

* app/airbrush.c
* app/pencil.c: Reorder code a bit in the tool motion function to
avoid executing unnecessary code in the case of a pixmap brush.

Other changes in the same commit:

* app/install.c: Make quote_spaces extern.

* app/appenv.h: Declare it.

* libgimp/gimpui.def: Add missing entry points.

* libgimp/makefile.{cygwin,msc}: Add missing objects to gimpui.